There are numerous doors that are vertically oriented in the closed position and store in an open overhead position that are used as doors for buildings and trailers.
One common construction is a tilting, non-flexible one-piece door. This type of door may be of generally two constructions. The first is a center pivoting door that uses a framework to which the door is mounted that pivots on a horizontal axis proximate to the vertical center of the door. These doors require space immediately adjacent to the door on the inside and outside for the door to open and close. The action of the door makes entrapment possible at the sides and bottom of the door. The second type of one-piece door uses horizontal and vertical tracks to guide the door between open and closed positions. These doors do not require clearance space adjacent to the outside of the door but require a considerable amount of clearance space to the inside of the door to allow the door to open and close. These doors present the same potential entrapment dangers as the pivoting door. These types of doors have been used on buildings but are not suitable as trailer doors in that the inside clearance space needed to open and close the door would significantly decrease the payload of the trailer. Further, if the cargo shifted during transit, the door could be jammed in the closed position.
Another common type of door is a sheet door. Sheet doors have flexible door panels that are guided around rotatable guide wheels between the open and closed positions. When in the open position, the flexible door panel is substantially horizontal to maximize the height clearance in the doorway opening. These doors are made from a flexible plate material that requires reinforcement at the edges. The flexible plate material must be formed into a pivot strengthening profile to give the door adequate strength and must use a rather large drive wheel to move the flexible plates from the horizontal to vertical tracks and from the vertical to horizontal tracks as the door is opened or closed. While increasing headroom or decreasing the hang down of the door into the door opening, these doors are somewhat flimsy and noisy to operate. Moreover, the inability to move the plates through a conventional transitional radius necessitates the use of large diameter drive rollers on either side of the door consuming significant interior space. The bending of the plates around the drive rollers causes undesirable stress on the plates and precludes tolerance to above-normal wind pressure.
Sectional doors are well known in the art. One concern with sectional doors, however, is the entrapment of hands or fingers at the interfaces of the door sections and along the edges of the door. Pinch-resistant sectional doors have been developed with integrally formed section interfaces that eliminate the finger and hand entrapping gaps, but these doors still require additional hardware to perform this function. Similar hardware may be added to a conventional sectional door to perform the same function. To prevent entrapment at the edges of the door, longitudinal mating sections have been added to pinch resistant sectional doors and conventional sectional doors.
As a further disadvantage, sectional doors generally have hinges and other hardware mounted on the interior of the door. If used as a trailer door, this hardware may damage cargo within the trailer or interfere with door movement. Attempts have been made to remove this disadvantage by designing doors with continuous hinges. Generally, these hinges are constructed of polymeric material and may be an integral component of the door or installed as a separate component between the sections. Although these hinge designs can be flush with the back of the door, the pivot point established by the hinge is fixed, thereby creating stresses in the hinge and the hinge attachment areas.
Rolling doors made from a plurality of slats or a sheet of metal suffer a similar buildup of stresses in the hinge because they also have a fixed pivot point. Rolling doors, however, have the advantage of pinch resistance because they are made of a plurality of closely fitting slats. But, due to the shorter height of the slats, a large number of slats are necessary to cover the door opening resulting in the rolling door being heavier and more expensive than sectional doors. These doors also require extensive headroom to store the rolled up door when the door is in the open position. The large number of slats also increases the time necessary to manufacture and assemble these doors. Assembly is complicated by the fact that these doors require the slats to be individually longitudinally interlaced. This interlacing also results in an interconnection which transmits force between slats so that even a localized impact can result in damage to a number of adjacent panels. While the slats are often constructed of sheet steel offering little insulation, additional plastic insulated materials and insulation covers have been added to these types of doors. As will be appreciated, the addition of plastic insulating material increases the weight and complexity of the door, thereby increasing the cost to the manufacturer and the time necessary to manufacture the door. Further, these rolling door designs normally have fixed pivot points with no provision for reducing stresses in the area of the hinges.
Some sectional doors have utilized polymeric materials for door components, including the door sections. In one instance, a door has been constructed of blow-molded polymeric material sections for use on building structures such as industrial, commercial, and residential garages. In another instance door panels having a polyurethane rigid core with a polyvinylchloride front skin and a non-metallic rear skin have been proposed. The rigid polyurethane core unitizes the two skins to make the panel section into a rigid lightweight structure. These known designs require expensive equipment of considerable size, particularly to process a double car width door section. Further, these doors contain conventional hardware such as stiles and hinges, which protrude into the area adjacent the interior surface of the door. Overall, the main difference between a conventional sectional door and these doors is the use of polymeric sections.
Sectional doors with sections from 18-24 inches in height necessarily have a relative angular movement between sections of up to 78° when traversing the transitional radius between the open and closed positions. These angular movements of the sections alter the force required to move the door and put stress on the hinge and hinge mounting area. It has been recognized that hinges with multiple bend points may reduce the stress on hinge elements as well as hinges having a plurality of co-extruded polymers to achieve a hinge capable of continuous movements of up to 90° or more. The extruded thermoplastic hinge has improved ability to withstand flexure cycles at room temperature as well as low temperatures. This hinge comprises a flexible cross-section of polyester elastomer and a co-extruded section of rigid or semi-rigid thermoplastic material. This type of hinge design is more costly and care must be taken during the extrusion process to assure adequate bonding or encapsulation of the different polymers used to produce the hinge.